Conventionally, as a bright pigment such as a pearlescent pigment, a pigment in which each of flaky particles such as mica flakes, synthetic mica flakes, silica flakes, alumina flakes, glass flakes, or graphite flakes is covered with a covering layer containing a metal oxide such as titanium dioxide or iron oxide, iron oxide particles containing α-iron oxide crystals as a main component, and the like have been known. Those pearlescent pigments glitter by reflecting incident light from the outside on surfaces thereof, and impart unique surface appearances that are varying and have beautiful effects to a coating surface when blended with a paint, to a drawn line or a printing surface when blended with ink, or to a surface of a resin molding when blended with a resin composition, together with color tones of various substrate surfaces thereof.
In order to enhance beauty, the pearlescent pigments have been used widely for various applications such as an automobile, a motorcycle, office automation (OA) equipment, a mobile phone, a household electric appliance, various printed matters, and writing instruments.
Titanium dioxide has three kinds of crystal forms including anatase, brookite, and rutile. Of those, anatase and rutile titanium dioxides have been produced industrially. Anatase titanium dioxide has a high photocatalytic activity, and hence accelerates the degradation of components and discoloration of a resin composition portion and a paint composition. On the other hand, rutile titanium dioxide has a photocatalytic activity that is about one tenth of that of anatase titanium dioxide and is suitable for being blended as a pigment with a paint composition or a resin composition.
Patent document 1 discloses a bright pigment including flaky particles and a metal oxide layer covering at least a part of the surface of each flaky particle. The flaky particles are formed of a material having a particle diameter corresponding to a 99% volume-cumulative particle diameter from a small particle diameter side, in a particle size distribution, of 48 μm or less and having a maximum particle size of 62 μm or less and a refractive index of 1.4 to 1.8. In the thickness distribution of the flaky particles, the frequency of the occurrence of particles having a thickness ranging from 0.8 μm to 1.9 μm is 90% by volume or more, or the frequency of the occurrence of particles having a thickness ranging from 0.01 μm to 0.35 μm is 90% by volume or more. The problems to be solved by the invention described in Patent document 1 are to prevent particles of various colors from being mixed to glitter due to the difference in thickness of respective flaky particles and to achieve both a satisfactory filtration property and a satisfactory coating film finishing property.